1. Field of Endeavor
The present application relates to microelectrode arrays and methods of fabricating microelectrode arrays, and particularly to a microelectrode array and method of fabricating a microelectrode array such as a neural interface with an integrated stiffening shank.
2. State of Technology
This section provides background information related to the present disclosure which is not necessarily prior art.
Micro-electrode neural interfaces are an essential tool in neuroscience, targeting the neuronal activity of neurons, enabling researchers and clinicians to better explore and understand neurological diseases. These interfaces use implanted neural probes to bypass damaged tissue and stimulate neural activity, thereby regaining lost communication and/or control with the affected parts of the nervous system.
The most common neural probes are thin-film micromachined probes fabricated on silicon substrates using MEMS fabrication techniques. Neuronal stimulation and recording is conducted at discrete sites (metal pads) along the probes. The metal pads are connected, via metal traces, to output leads or to other signal processing circuitry. Silicon is the most widely used substrate for this type of probe because of its unique physical/electrical characteristics. The prevalence of silicon in the microelectronics industry ensures the neural probes can be relatively easily and efficiently fabricated in large numbers utilizing common MEMS fabrication techniques. There is, however, concern regarding the suitability of these silicon-based neural probes for long-term (i.e. chronic) studies as the silicon will corrode over time when implanted in a body. Furthermore, the continuous micro-motion of the brain can induce strain between the brain tissue and implanted electrode promoting chronic injury and glial scarring at the implant site. Therefore, there are outstanding questions regarding the long-term safety and functionality of these silicon-based neural probes.
Polymer-based neural probes are an attractive alternative. First, they are flexible, thereby minimizing strain between the brain tissue and the implanted probe. Second, they are fully biocompatible and thus suitable for chronic implantation with no loss of functionality or safety. Finally, these polymer-based neural probes can be easily fabricated in large numbers using existing microfabrication techniques.
Unfortunately, the inherent flexibility of the polymer-based neural probes means the probes also have a low mechanical stiffness causing the devices to buckle and fold during insertion. To counteract this, separate stiffening shanks are typically fabricated and then attached to individual neural probes. This procedure is very time-consuming, and in most cases, where the stiffening shanks are extremely thin (<50 μm thick), also very difficult.